If I am calling to someone (I am using the regular PSTN) and he is using
an IP phone it is seamless from your end. His PSTN-VoIP gateway will
convert the signaling and voice samples from the PSTN based protocols to
VoIP based protocols and vice versa.

VoIP Network -------|GW|------ PSTN

The risk here is to abuse the gateway from the PSTN side (GW/IP PBX). If
you get yourself on the GW/IP PBX that’s it...

I have read the particulars to VOIP and securing
VOIP as an application. However, has anyone
performed any pen testing or research on using VOIP
as a gateway?

For example, someone from the outside (not part of
the VOIP network) dialing from home (etc) to an
organization's VOIP-enabled phone. Then, using the
VOIP-enabled phone as a gateway to the rest of the
IP network?

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----------------------------------------------------------------------------
This list is provided by the SecurityFocus Security Intelligence Alert (SIA)
Service. For more information on SecurityFocus' SIA service which
automatically alerts you to the latest security vulnerabilities please see:
https://alerts.securityfocus.com/